Is hitting fuel cut bad for the car? Ive heard it is bad (For some reason especially on the #4 cylinder.. this doesnt make sense to me considering fuel cut cuts fuel and spark from all cylinders but anyways...). Does it really harm anything if I hit it repeatedly? I am really curious and also, if is does please let me know why it would. Thanks

 

Good question. It could be considering it is so violent. But, I doubt it. Fuel cut is actually a safety measure used by the ECU whenever it sees too much airflow. So even though it sucks, it can save you from blowing up your motor.

 

Do you know what triggers the fuel cut on and evo? ie a sertine boost pressure of what?

 

Fuel cut happens when u fly into the red and dont shift. N E ways not much power past red on stock so might as well shift beforehand

 

Thank you mrmefodman. So it is just over rev protection. Thanks again

 

Fuel cut happens when the ECU detects too high of an airflow signal from the MAF. It has nothing to do with "revving". The only way to eliminate fuel cut is by altering the airflow signal in some way (flash, AFC, standalone, ETC).

 

Thank you mike.

 

Adding to what Mike said, fuel cut is also dependent on the outside air temp and pressure. It occurs at 1700 Hz Karman value at 20°C and 1000 mbar atmospheric pressure approx. That is roughly 1.2 bars relative boost pressure. That is why we see more owners reporting fuel cut as the temperatures go lower in the northern part of the country.

There is a separate safety feature for excessive RPMs. (Rev Limiter). It occurs in mine at about 8200 rpm.


Speedlimit....

 

Well... I am talking about my fuel cut which is nothing to do with a rev limiter... It cuts out hard at around 4500 rpm and if I stay on the throttle it will sooner or later pull out of it (It hits hard so I only have held it a few times). I is obviously nothing to do with a fixed amount of airflow. I have hit much higher hertz at 7k than at 4500 obviously so I guess I would wonder why it hits my car at 4500 rpm and is it bad and harmful to the car or is it ok?

 

Check for boost leaks.

 

If I lean it out a few percents it doesn't cut out... I am quite sure it is fuel cut. By leaning it out with the AFC the ECU sees less airflow therefor I guess doesn't think it should cut the gas. I never did any type of leakdown test on the car but nothing is loose and it spools instantly, holds pressure fine and does seem to be leaking (But who knows). At any rate.. I am pretty sure this is fuel cut. Is it harmful and why does it cut out at usually 4500rpm. I heard Buschur had this same problem on thier dyno test car.

 

If it feels like you hit a brick wall, it is fuel cut. The transient on the drivetrain resulting from fuel cut cannot be good for the car if repeated many times. The best way is to install proper supporting mods then add an ECU flash or aftermarket ECU to remove fuel cut. Or you can always turn down the boost.

Speedlimit...

 

I thought my car kept hitting fuel cut also (and right around 4500 rpm's, usually in 3rd) but come to find out, the plugs just needed to be replaced. Put in some new plugs (don't go to the dealership for them) and the car is fine.

 

Wow, I was going to type almost the exact same thing.

I had very similar things last winter, with the hiccup or stumble that would vary in severity at approx TQ peak (~4500 rpm). I called it boost cut and fuel cut, but I think it was really misfire. I definitely did not hit 1700 HZ Karman per my SAFCII, highest readings were around 1600 or less, but leaning out on SAFC did help for awhile, which is why I thought it was fuel cut. Over time, leaning did not help anymore, but switching from Denso IW24 back to stock plugs did help. Then it started happening again, so I switched to NGK Coppers that are gapped tighter (approx .026) and I have not had the problem at all. I think leaning helped since the mixture was too rich and contributed to misfire. Also, the plugs seemed to be fouled from running so rich.

It makes the car soooo much nicer to drive and so much smoother now that it pulls through that rpm range. It was such a pita and it sucked not knowing if it would start bucking at that rpm or not...

On a side note, replacing my stock flex hoses with Samco, stock hose clamps with TBolts, and cleaning out the MAF and MAF tube also helped for awhile (before I switched to plugs). Perhaps this fixed a leak that made the mixture leaner since more air made it to the motor?

Take care,

FB

 

Hmmm.... I wish I knew what was truly happening. It never throws a CEL when it happens. It USUALLY happens right around 4500 RPMs. It will pull out of it if I stay on the gas. The car still has the stock plugs and only got 6,500 miles (Don't see why I would have screwed a plug already). When I lean it out a little bit it goes away and never came back but I hate to lean out my car at all with no datalogging stuff. So who thinks it is fuel cut and who thinks it is a missfire (It hits HARD.. like you cut the motor for a few seconds.. not a little hiccup).